ARCHEODRONE Drones for archaeological surveys

ARCHEODRONE Drones for archaeological surveys FEDER - Presage 37827 Archéodrone is part of the "PAST (Plateforme Archéosciences Toulouse)" technical platform, attached to the TRACES Laboratory (CNRS – University Toulouse – Jean-Jaurès (France). This platform consists of drones (fixed-wing and rotary wing aircraft) and various sensors (digital conventional & infrared cameras, Lidar) used in archaeological surveys,from the site scale to the territory scale. Comparing to airplane, the use of drones permits low altitude, high resolution, and repeated acquisitions of spatial data useful to archaeological detection and 3D site documentation. Lowering the level of observation Better spatial resolution Flexibility of using Accessing difficult places 150 m 3D (Photogrammetry & LiDaR) Infrared Imagery Airborne thermal survey is based on the principle that there is an essential difference in thermal characteristics of archaeological remains relative to the sediment in which they are buried. Therefore, archaeological structures tend to react differently to changes in temperature compared to sediment banking, warming or cooling more or less quickly depending on their nature. This method of detection is used since the 1970s in archeology. But the use of the aircraft made this method difficult to access, because of its cost and lack of organizational flexibility. The implementation of a thermal camera on a drone allows to reduce these defects. More widely, the use of multispectral sensors allows to detect various forms of vegetation hydric stress. A test of UAV airborne thermography was made in Berry (France) in order to test the potential of cereal hydric stress for the detection of buried archaeological sites. A survey carried out over a parcel which delivered antique material without any concentration has revealed a thermal anomaly probably due to moisture stress on plants, and invisible ona conventional picture. The limits of this anomaly being quite distinct in space, one might think it reveals the exis tence of anthropogenic developments now buried. «Conventional» Imagery Aerial photography is used in archeology since 1880. It consists in photographing open areas at a medium altitude, and interpreting changes in soil color and / or development of vegetation by the presence of buried archaeological remains. Aerial photography is also used for vertical shooting of visible archaeological structures. The advantage of the drone in conventional photography is to document areas of difficult access. On the site of "Silla del Papa" (Bolonia, Spain), it was to make a statement by drone shooting of a set of Bronze Age settlements installed against a cliff, only visible by negative marks (floor blocking holes, drainage gutters, etc.). This set is difficult to access by the height of the remains (up to 20 m high). Photogrammetry - or image matching by dense corrélation - provides 3D models from uncalibrated digital images. Dedicated softwares can automatically find areas of correlation in several pictures of the same scene, and extract a 3D model. The software Agisoft Photoscan was chosen to perform this automatic extraction. The medieval village of Flaugnac (Lot, France) was over flown by a drone equipped with a digital camera. All images were processed in Agisoft Photoscan, allowing the extraction of a Digital Elevation Model (DEM). LiDaR (Ligtht Detection and Ranging) measures the height of the ground surface and other features in large areas of landscape with a very high resolution and accuracy. Such information was previously unavailable, except through labour-intensive field survey. Because lidar uses light beams, it has the potential to penetrate gaps in the woodland canopy and so record the ground surface under the trees. This can reveal features that would not otherwise be seen. The spanish site of «Silla del Papa» was covered by Lidar, revealing all the details of the topography. Photogrammetric 3D model of the medieval village of Flaugnac (top) & LiDaR Scanning of «Silla del Papa» (down) All points & Digital Surface Model (left) / Ground points & Digital Terrain Model (right) Conventional picture (top) and thermal image (bottom) On the site of the ancient roman town of Baelo Claudia (Bolonia, Spain), The aim was to perform a vertical shooting of a necropolis. These photographs provide an overview of the necropolis, a precise map of visible remains, and indices for the presence of buried structures. Nicolas Poirier nicolas.poirier1@univ-tlse2.fr Carine Calastrenc carine.calastrenc@univ-tlse2.fr Florent Hautefeuille http://blogs.univ-tlse2.fr/archeodrone/ Vertical picture of the roman necropolis of Baelo Claudia